The main aim of the research is to find out the leading cause of depletion of the population of the Mary River Tortoise otherwise known as the Mary River Turtle. The Mary River Tortoise has been classified as an endangered species, which faces several threats to its existence. This study aims to narrow down to the leading cause of reduction of the population of the Mary River Tortoise. The Mary River Tortoise is one of the species that faces extinction from a variety of threats most of which have been attributed to human activity. The impact of this study will be to aid legislators and conservationists to establish means of further preserving the numbers of the Mary River Tortoise by safeguarding it against the risk or risks identified.
The Mary River Turtle rose to prominence primarily between 1970 to 1990 for its popularity in the pet trade. Pet store owners purchased it under the name of the common saw shelled turtle Elseya latisternum (Georges & Thomson, 2006). Its hatchlings were referred to as the Penny turtle, as further observed by Georges. Legal trade of the Mary River Turtle had been stopped in 1974, but the sale went on under cover of the with the false description. Venders refused to give up the location they found the turtle. In 1990, John Cann picked up four adult specimens of the turtle and they were officially described as a new genus and species in 1994 (Cann & Legler, 1994). The Mary River Turtle was subjected to the commercial plunder of its eggs in the years after 1970. In addition, the construction of dams and weirs affected its ability to relocate freely within the river. The study topic is important in establishing the most significant threat to the Mary River Turtle and subsequently to enable ecologists to strategize on the best way o preserve the endangered turtle.
The Mary Rive Turtle is a species that is endemic to the Mary River in south-eastern Queensland (Gouraud et al., 2004). It has a range of about 262.8 km from the mouth of the river to the area 59.3 km upstream of the river (Cann &. Legler, 1994). The Mary River Turtles population density is considerably below that of other turtles that share the same habitat (Elseya sp. and Emydura krefftii) (Flakus, 2002). The Mary River Tortoise accounted for only 14% of turtles caught in a systematic population monitoring exercise carried out by Flakus (2002). The species has been identified to be a rare find in all its known habitats (Cann, 1998).
It has been noted that there has been a significant decrease in the population of breeding female Mary River Tortoises of around 95% between 1970 and 2000 (Flakus, 2002). In the 1960s and 1970s, there were hundreds of females nesting in the banks of may River near Tiaro. However, for the same period between 1998 and 1999, there were only ten nested in the same region (Tucker, 1999).
Similar to other turtles that respire through the cloaca, the Mary River Tortoise prefers to stay in flowing, well-oxygenated parts of streams. Its ideal habitat is riffles, especially the most productive parts of a river that are shallow but have fast-flowing, aerated water) and shallow expanses that interchange with deeper, flowing pools (Cann, 1998). It is hardly ever to be found in impoundments, according to (Bohm et al., 2013). For the juveniles, the available data though not definite, suppose that they are commonly found in rocky areas with sand or gravel on the riverbed with different depths of water. For instance, Bohm et al., discovered a hatchling at a crossing in 10 cm of water (2013). Adults prefer regions with shelter below the water surface. These areas include, sparse to dense macrophyte cover, submerged logs and rock crevices. However, many times, the adults come out to bask in the sunlight. Cann further observes that some turtles have been found out resting in sites with little aquatic vegetation or submerged logs (1998). The Mary River Turtle can also stay underwater in depths that vary from below a meter to more than 5 m (Bohm et al., 2013). .
However, the population of the Mary River Tortoise has been documented to be on a steady decline. Despite limited data on nesting habits, there has been a general observation of a decline in sightings by tourists, locals and conservationists alike. This has brought to fore the need to identify clearly the reason to be attributed for this phenomenon.
Limited data exists on the prevalence of the Mary River Tortoise upstream and in the tributaries. The Mary River is served by several tributaries, for instance, Tinana Creek, Munna Creek, Obi Obi Creek, Yabba Creek, Wide Bay Creek and the Susan River. There has been little or no research done to establish the presence of the Mary River Tortoise on these tributaries. This information would serve to provide ecologists with more specific data on the prevalence of the tortoise and aid in conservation measures targeting endangered animals. In addition, there is limited data on the nesting habits of females during and after laying eggs. Little is known of the measures that females take to identify the best suitable spot for nesting. Lastly, there is limited data on the habits of juveniles. There is need to carry out a study on the lives of juveniles in order to establish the way of life for them.
For this observational study, the researcher is interested in answering the question of the most significant threats to the lives of the Mary River Turtle. Various factors are affecting the prevalence of the Mary River Turtle. However, predators, angling, water pollution and dams were hypothesized to be the most likely causes of depletion of the Mary River Turtle. The study aims to find out whether the presence of predators, human activity through angling, water pollution, and building dams leads to depletion of the Mary River Turtle.
The experimental animal for this case would be the Mary River Tortoise also known by another common name the Mary River Turtle or scientifically, Elusor macrurus. It is listed as endangered under the Nature Conservation Act 1992 (Queensland). It is a dark brown turtle with a rusty red-brown to almost black top, with a greyish underbody. The shell is quite broad and has a notch in the middle (Thomson et al. 2006). It has either a cream or a yellow plastron. On the lingual areas, the turtle has pinkish-white smudges, and the dorsal skin is grey. This species is also characterized by pointed tubercles on its neck. As Berry and Shine (1980) observe, the males are significantly larger than the females, which is a distinguishing fact considering all other turtle species in Australia have larger females. Males are approximately 42cm long and females length is about 34cm. Females have their shells wider at the front than at the back. Males have their shells narrow and with straight sides. The species has physiological adaptations that make it aquatic and a fast swimmer. It displays cloacal respiration (Flakus, 2002). The hind feet are considerably huge, and it can swim rapidly.
An observational study would be carried out to investigate the purposes of this project. The study will be carried out on the Mary River on five different locations along the river. These locations will be selected based on their previous history with the presence of the Mary River Turtle. Samples will be selected based on the criteria for selection of a quantitative study. The target population will be selected. The target population is the Mary River Tortoises within the five locations identified. The population was then sifted for the accessible population. An eligibility criterion was developed based on gender and age. Females and males both have to be above a year old.
Five turtles, three male and two female will be captured from each location and a waterproof chip attached to its hind limb. The turtle will then be released into the wild in order to study its behavior for three months. The movement of the chip will be tracked on a daily basis, and if the chip does not move for a whole day, it will be tracked in the field. After three months, the results will be compiled and analyzed then the remaining turtles will be monitored for another three months. The cycle will be repeated continuously for twelve months in intervals of three months.
In the event a tracker does not change position for more than 24 hours, the exact position of the tracker will be established in order to find and observe the matter with the turtle. This will be the manner of establishing live and dead turtles.
Expected results and Significance
The number of turtles is expected to fall from the initial due to the factors that have been established to negatively affect the life of Mary River tortoises. The cause of death could be either predators, angling, inability to breathe in polluted water, or the building of dams.
Predators- The Mary River Turtle has low hatching success due to the presence of predators such as foxes that prey on the eggs before they hatch and immediately after they hatch. In addition, goannas and illegal collectors pick the eggs hindering the success rate of the breeding process.
Dams and Weirs- these provide poor quality habitat for the Mary River turtle. To begin with, the collection of water indicates a possible decline in the quality of water. Consequently, there is less dissolved oxygen, and the turtles have to keep resurfacing for air which leads juveniles especially to susceptibility to predators. In addition, the main aquatic insect larvae that juvenile Mary River Tortoises feed on are mainly present in shallow riffle waters. Consequently, the turtles lack food.
Dams and weirs also destroy the natural nesting habitats for Mary River turtles. The dams and weirs flood the nesting sites excessively making them inaccessible. Consequently, the turtles are forced to nest in new and possibly unsafe areas.
Turtles are also hurt and can be fatally injured during high water flows due to excessive abrasion and shearing against the sluice when they go over the top of dam walls. In some instances, the turtles are washed downstream and are unable to return upstream. In the event that a Mary River Tortoise is washed up into the estuary over the top of the Mary River Barrage, they are highly likely to be stranded and killed by the salt water.
Anglers and illegal egg collectors have hampered the breeding and reproduction efforts of the Mary River turtle. The turtle is reduced significantly in population due to the collection of eggs. No efforts are made to recruit the eggs that have been retrieved. Consequently, the turtle population continues to dwindle.
The anticipated outcomes will be vital in the conservation efforts to protect the Mary River turtle. Measures can be identified that protect the habitat, bar predators and anglers from accessing the eggs and other mitigation measures to preserve the Mary turtle species. In addition, determining its population dynamics will enable the conservationists to create a supportive environment for the turtle to develop in its niche. In addition, measures such as reduction of pollution will not only benefit the turtle, but also other organisms in the same ecosystem. Lastly, a study of the conditions in which the turtle lives will be important in the event an artificial habitat is created. This will enable the conservationist to understand the ecological needs of the turtle.
Berry, J. F., & Shine, R. (1980). Sexual size dimorphism and sexual selection in turtles
(Order Testudines). Oecologia, 44(2), 185-191.
Bohm, M., Collen, B., Baillie, J. E., Bowles, P., Chanson, J., Cox, N., ... & Cheylan, M.
(2013). The conservation status of the worlds reptiles. Biological Con...
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